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<h1>Plantilla</h1>

<p>Many builders build their guitar on a carved solera to create a domed top (and back). The arch in the top allows to wood to shrink or expand to a certain extent without developing cracks. Also it is said that an arched soundboard is under tension, which has a positive effect on the sound. But more important: The dome height is an integral part of the instrument geometry (neck angle, string height at nut and 12th fret, fretboard thickness, fret height, scale length, bridge and saddle height, and dome height). </p>

<p>The shape of the dome is usually chosen to be a section of a sphere, with a radius of about 25 to 28 feet (7620 to 8534 mm). Rik Middleton specifies a radius of 2.3 m in his book on page 45 <a href="../appx/references.htm#001">[1]</a>. This is schematially outlined in figure 44 below. </p>

<p class="imgbox"><a name="fig-044"></a><img src="../img/fig-044.png" style="max-width: 400px;"/><br />Figure 44: Cross-section through the body centerline of the carved solera.</p>

<p>The dome radius in figure 44 has been drawn dramatically shorter in order to fit on the screen. This makes the dome appear much higher. In reality, the dome height is only a few millimeters.</p>

<p>An arched soundboard creates a constructional problem: The height of the ribs is no longer constant. The sides are higher near the center (in the waist area), and somewhat lower farther away (at the upper and lower bouts), and lowest at the end and neck heel blocks. If the shape of the dome is a circle (or sphere in 3D), we can use a "simple" radius disk to sand the edges of the ribs and linings down to the exact heigt profile required for the body shape.  Additionally, the angle of the contact (glueing) area between sides and top automatically gets the correct angle.</p>

<p class="note">Another complication occurs from the back-spring effect of the board-struts assembly. The initially flat soundboard is positioned over the dome, then the preshaped struts are glued into position and cramped down, so that the soundboard is pressed into the shape of the dome. The problem is that, after a sufficient drying period, the board springs back a little bit, which effectively <em>reduces the dome height</em> by an unknown factor. This spring-back must be taken into account, it can be compensated by correcting the neck angle accordingly.</p>


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